I be

can i say :
It will happen if i be with my friends

and why do we use “be”

We don’t use ‘be’ in that sentence, Abdalhadi.

It will happen if I am with my friends.
It would happen if I were with my friends.

could you use " be " in a sentence

I want to be a teacher.
Be faithful to your wife!

There is also a subjunctive, as in this Leonard Cohen song, but it is not much in use nowadays:

If it be your will
That I speak no more
And my voice be still
As it was before,
I will speak no more…

thank you

to be or not to be ? this is the question. (Hamlet)
What is to be done?

Is your sister in class today?
she might be.